Liquid crystal displays (LCDs) are increasingly being used for the display device in televisions, personal computers, and much state-of-the-art equipment, such as automotive navigation systems and simulation devices. One particular area where LCDs are increasingly being utilized is flat panel televisions. With the general acceptance of flat panel TV technology, there has been a large marketing and technology war over which technology is best, such as plasma display technology versus LCD display technology. Flat panel televisions are judged on thickness, weight, price, product lifetime, and image quality. Certain display technologies may be better in one area, such as image quality, but worse in another area, such as weight or price.
Typically, the image quality of a particular display technology is one of the most important factors taken into consideration when a buyer purchases a flat panel television. There are many different criteria to judge image quality. Two important criteria are contrast ratio and black-level reproduction. In the past, the contrast ratio and black-level reproduction of plasma displays have been better than those of LCDs and plasmas displays have often been judged to have better image quality reproduction than LCDs.
An image is generated on an LCD by controlling the amount of light that can pass through an LCD material. The light can be provided by a backlight located on one side of the LCD where the image is viewed from the other side of the LCD opposite the backlight. Typically, the LCD material can include a large number of pixels arranged in an array where the pixels can be individually controlled to affect an amount of light that passes through the LCD material. The pixel control can reproduce a desired image.
One limitation of LCDs is that it is difficult to completely turn off a pixel at a particular location like in a cathode ray tube (CRT). In a CRT, the electron beam can almost be completely turned at a particular location to generate a deep black. In an LCD, a typically image includes light and dark pixel areas. When the backlight remains on to light the lighted pixel areas of the image, light can also bleed through the dark pixel areas, which limits the blackness in the dark pixel areas. One approach to improving the black levels in an LCD panel is to block the light that leaks through the LCD panel when a pixel is supposed to display black levels. Light blocking technology is complicated and its success has been limited. Thus, it would be desirable to provide alternative methods and apparatus, in place of or in conjunction with the light blocking technology, that can be used to improve image quality, such as contrast ratio, generated using an LCD display.